The interaction of thermal H and D atoms with thin ion-beam deposited
C : H films were studied with vibrational (HREELS) and Auger electron
spectroscopy. At surfaces which exhibit aromatic sp(2) CH groups a hyd
rogenation reaction towards sp(3) is observed with a cross-section of
4.5 Angstrom(2). At fully hydrogenated C : H surfaces with solely sp(3
) CH groups present, H abstraction towards molecular HD occurs at D im
pact with an initial cross-section of 0.05 Angstrom(2). The magnitude
of both cross-sections is in line with an Eley-Rideal mechanism. As a
radical C atom is produced by the H abstraction reaction, a thermally
activated de-excitation via a hydrocarbon radical split-off is initiat
ed which causes chemical erosion of the C : H film at a yield of about
0.01 C per incoming H around 600 K.